[clang-tidy] Reject malformed -std spellings in check_clang_tidy.py. NFC. (#195609)

zeyi2 · web-flow · commit e01ea6ce1264 · 2026-05-07T07:49:08.000Z
`check_clang_tidy.py` expanded any `-std` value containing `-or-later`,
even when extra text followed the suffix. e.g. `c++20-or-latermisc` was
treated like `c++20-or-later`.

This commit requires `-or-later` to be the actual end of the spelling
before expanding it, so malformed values are passed through and
diagnosed by clang.
diff --git a/clang-tools-extra/test/clang-tidy/check_clang_tidy.py b/clang-tools-extra/test/clang-tidy/check_clang_tidy.py
@@ -460,7 +460,11 @@ def run(self) -> None:
 
 
 def expand_std(std: str) -> List[str]:
-    split_std, or_later, _ = std.partition("-or-later")
+    split_std, or_later, suffix = std.partition("-or-later")
+
+    if or_later and suffix:
+        # Keep malformed -or-later spellings unchanged so clang diagnoses them.
+        return [std]
 
     if not or_later:
         return [split_std]
